In such apparatus the milk line system has to be periodically cleaned to prevent milk discharged by the milk line system from being contaminated and hence from deteriorating. In the conventional milking machines, the line system is cleaned after the herd has been milked. In the case of automatic milking by milking robots, the milk line system is cleaned after a certain period of time has elapsed or a predetermined number of animals has been milked. The milk line system may also be cleaned when it has been ascertained that milk produced by an animal which is infected with mastitis or another condition that adversely affects its milk is discharged by the line.
The cleaning of the milk line system is divided into three phases, the pre-rinsing, the main cleaning and the post-rinsing. The pre-rinsing serves to remove the milk residues as much as possible from the system prior to the main cleaning. Consequently, the main cleaning will require less detergent. In order to achieve this, the pre-rinsing should not be a circulation rinsing. For the pre-rinsing the temperature of the water is 40.degree. to maximum of 60.degree. C. (104.degree. F.-140.degree. F.). The pre-rinsing is succeeded by the main cleaning. The main cleaning serves to clean and disinfect the equipment. This is realized by circulating a cleaning fluid. The cleaning is mostly effected with an alkali having a cleaning or disinfecting function or both. In order to avoid formation of scale in the milk line system, said system has also to be cleaned from time to time with an acid. With the acid, scale formed in the milk line system, such as on the electrodes of a milk conductivity sensor, can be dissolved and thus removed from the milk line system. After the main cleaning, the milk line system has to be cleaned by means of post-rinsing. This is to prevent residues of the cleaning fluid from coming into the milk. The post-rinsing is effected with tap water. The post-rinsing water should preferably not circulate.
In practice it has been found that mistakes occur during cleaning of the milk production equipment, as a result of which this equipment is cleaned insufficiently and consequently the germ count of the milk more than doubles. This may be caused by an insufficient quantity of alkali or acid, or by insufficient post-rinsing, or by the fact that certain places are not reached by the cleaning fluid, because a tube is pinched off, etc.